Mixtures of oxygenated acyclic terpenes



United States Patent 8 Claims. or: 260-489) This application is acontinuation-impart of application Ser. No. 182,924, filed Mar. 27,1962, now abandoned.

This invention is concerned with a process for the production ofoxidation products, in particular from unsaturated compounds.

The photosensitized oxidation of certain hydrocarbon compounds, whichcontain a double bond, using molecular oxygen as oxidizing agent, isknown. [For example, according to the information given in German Patent933,925, e-pinene may be oxidized in the presence of sensitizingsubstances to form p-inocarveyl hydroperoxide.

The direct reaction of oxygen-containing acyclic terpenes of thefi-citrolellol type related compounds in the presence of light is alsoknown. This reaction leads in most cases, with a partial alteration ofthe functional group, to a large number of reaction products or in partto a non-specific degradation and thus to the destruction of the carbonskeleton. Thus, among the oxidation products of citronellol, citronellicoxide and dihydroxy citronellol have been identified in addition to acidfractions, CO CO and H (R. Dupont, Ind. chim. belge ll, 3 (1940); CA.34, 2353 (1940), while its aldehyde, citronellal, changes intomen-thone, isopulegol, ketone C H and dihydroxycitronellic acid and inaddition decOmpOses into molecular fragments that is fl-methylhexylicacid, fl-methyladipic acid, acetic acid and acetone (Sernagiotto, AttoR. Accad. dei Lincei, Rome (5) 24 (19-15), 850.)

By comparison with the first mentioned pure hydrocarbon compoundsalready proposed for photosensitized oxidation, the compounds of thecitronellol type are characterized by the fact that they contain otheroxidation-sensitive groups, for example primary or secondary alcoholicgroups, in addition to at least one double bond. One cannot predict inwhat manner these acyclic terpenes will behave on photosensitizedoxidation or quite generally what should be the behaviour of compoundswhich contain such oxygen-containing functional groups as well as adouble bond. However, it was to be expected in every case that anattempt at such an oxidation would result in not only the double bondbeing attacked but also the oxidation-sensitive functional group. Themarked susceptibility to oxidation of for example an alcohol or aldehydegroup is of course known.

it has, however, surprisingly been found that photosensitized oxidationwith molecular oxygen, known per se, for example from German Patent933,925, can be specifically applied to the oxidation of thoseethylenically unsaturated systems with allyl-hydrogen atoms theallyl-oxidizable double bonds being advantageously not in a terminalposition, one perhyd'roxyl group being introduced with simultaneousallyl transposition by displacement of the double bond towards theformer allyl position, without the simultaneous production of oxidationreactions which would otherwise be expected to be formed by reactionwith functional groups which are generally readily oxidizable.

The subject of the invention is a process for the photosensitizedoxidation of ethyl-enically unsaturated compounds with molecular oxygenand with initial introduction of perhydroxyl groups onto one carbon atomof the double bond and simultaneous displacement of the double bondtowards the allyl position and, if desired, subsequent reduction ofthese oxidation products of the first stage, and is characterized inthat with selective oxidation on the CC multiple bond, there aresubjected to the process those unsaturated compounds which containoxygen-containing groups as well as at least one C-C double bond theoxidation products so formed being if required reduced in a manner knownper se.

Particularly suitable starting material for the process of the inventionare those which contain oxidation-sensitive oxygen-containing functionalgroups and are at least ethylenically unsaturated in one position.Examples of such starting materials are unsaturated alcohols, aldehydes,ketones, carboxylic acids and their derivatives such as esters or thelike. As starting material acyclic terpenes such as (If i Ic Ia whereinR is a member selected from the group consisting of hydrogen, acyl,straight and branched chain saturated and unsaturated aliphatichydrocarbons, hydroxy, and alkoxy, R and R are each a member selectedfrom the group consisting of hydrogen, straight and branched chainsaturated and unsaturated aliphatic hydrocarbons, and R is a memberselected from the group consisting of hydrogen and acyl.

By the process according to the invention, that is with oxidation at thedouble bond and simultaneous displacement of the double bond into theallyl position, an additional oxygen-containing functional group isintroduced into the carbon structure without requiring changes byoxidation in the oxygen-containing groups which are already present. Thefact that this process produces results which were to a high degreeunexpected is immediately apparent if the known sensitivity to oxidationof the aldehyde group is considered. The specific effect of theoxidation process according to the invention is emphasized by the factthat an undesired oxidation at the oxygencontaining functional group canbe avoided even in the presence of this group which is extremelysensitive to oxygen.

The oxidation process can be carried out in a manner known per se. Thepresence of photosensitizers which transfer oxygen is essential. Suchphotosensitizers are substances which absorb photochemically actingquanta without undergoing a permanent chemical change. Suitablephotosensitizers include classes of substances which are able tophotosensitize the ascaridol synthesis from the a-terpinene (G. A.Schenck and K. Ziegler, Naturwissenschaftcn 32, 1957 (1944)) or totransfer oxygen to tetraniethyl ethylene. The sensitizing additives areusually dyestuffs such as Bengal pink, Sudan-G, methylene blue,chlorophyll, Eosin, zinc tetraphenylporphine, dinaphthylene-thiophene,thionine or highly annellated (large number of rings) aromatichydrocarbons which absorb light filtered through glass, more especiallyin the range of about 350 to 590 mg.

The photosensitized oxidation is carried out according to the inventionin the presence of gaseous oxygen or gases containing the latter, forexample air, and simultaneously the reaction mixture is exposed to asource of artificial or natural radiation which can emit light, moreespecially in the range from about 350 to 590 me. The reaction accordingto the invention is in particular carried out in the presence of lightwhich has been transmitted through an ordinary glass filter in order toeliminate undesired short-wave ultra-violet components of the light.

The oxidation process can with advantage be carried out in solvents.Suitable solvents are for example alcohols, preferably lower alcohols,in particular methanol, ethanol or propanol. The use of solvents mayhowever be disposed of in certain cases. The compound to be oxidized isthen reacted together with the oxygen-containing gas in the presence ofsmall quantities of sensitizer in a reaction apparatus in which therequired light of an artificial or natural lighting source is used tobest possible effect. With artificial lighting sources, it is generallymost desirable to arrange the light source inside the reaction apparatusin such a way that all the available light beam is irradiated into thereaction material. In this way, the unsaturated compounds add exactly 1molecule of oxygen for each ethylenic double bond with practicallyquantitative formation of hydroperoxides, and with complete protectionof the functional group which simultaneously is present. The formationof hydroperoxide proceeds in such a way that 1 molecule of oxygen isadded to one of the two carbon atoms of the double bond. Simultaneously,the double bond is shifted into the C-C single bond adjacent the othercarbon atom of the double bond, so that the double bond, after theformation of hydroperoxide, is in the allyl position to the introducedoxygen. In principle, the entry of molecular oxygen with formation ofhydroperoxide can take place on one or the other carbon atom of thedouble bond to be oxidized.

It has been found that with compounds such as can be employed inaccordance with the invention, i.e., starting materials and namelyacyclic terpenes containing both at least one double bond and anoxygen-containing functional group particular features result if such anoxygencontaining group is present on a C-C double bond. For example, ifcompounds are used in the process according to the invention with whicha carbon atom adjacent the double bond is simultaneously combined withan oxygen atom, that is to say, if the double bond is for examplepresent in the allyl position to the oxygen-containing group, then thisdouble bond will normally not be affected by the photosensitizedoxidation. T he oxygencontaining group can therefore exert a protectiveaction on the double bonds immediately juxtaposed thereto. This fact canbe utilized with advantage in the process according to the invention, inthat compounds unsaturated in more than one position, with which thereis at least one double bond which is largely insensitive to the actionof oxygen under reaction conditions, are selectively oxidized in atleast one additional double bond situated at another position withoutsimultaneous oxidation of the first-mentioned double bonds.

The hydroperoxides formed according to the invention as first-stagereaction products can thereafter be subjected to a reduction inaccordance with a further feature of the invention. Thus, it is possiblefor the hydroperoxide groups to be reduced in a manner known per se tothe corresponding alcoholic groups. This reduction can for example beeffected with sodium sulphite e.g., by treatment with a saturatedaqueous sodium sulphite solution, by treatment with triphenyl phosphinein the cold or by treatment with other reducing agents known per se, forexample, complex alkali aluminum hydrides such as LiAlH If theoxygen-containing functional group which is originally present exists ina higher oxidation stage, then in accordance with a further embodimentof the invention, this other oxygencontaining group can also besimultaneously or subsequently reduced. It is possible in this way toprepare, from unsaturated oxygen-containing compounds, polyfunctionalalcohols which contain one OH-group more per oxidized double bond, bycomparison with the functional oxygencontaining groups of the startingproduct. The process according to the invention is more especiallysuitable for the production of glycols from simple unsaturatedmonofunctional oxygen-containing compounds, the fact that they stillcontain the original double bond even though it is displaced by oneposition in the carbon chain being characteristic of these glycols. Theprocess of the invention discloses the possibility of obtaining, bysynthesis, compounds which otherwise are comparatively difficult toobtain, which compounds are of industrial and economic interest in manyrespects.

The process of the invention is more especially suitable for thephotosensitized oxidation of compounds from the class comprising acyclicterpenes, such as can for example be obtained from turpentine oil.Typical representatives of compounds from the class of acyclic terpeneswhich can be oxidized according to the invention are compounds such asare characterized by the Formulae I, Ia, Ib, Ia, and Id set out below.In these general formulae the radicals R and R represent in particularhydrogen or saturated or even unsaturated alkyl radicals. The radicals Rand R can be the same or different radicals. If alkyl radicals arepresent, then these are preferably lower alkyl raidicals, advantageouslythose containing up to 6 carbon atoms. Typical representatives of suchacyclic terpenes which can be subjected to the process according to theinvention are the following:

General Formula I:

B-citronellol: R --R =H B-citronellyl acetate: R +R =H R3=(H3CH3 o2,6-dimethyl-2-nonene-8-ol: R =CH R +R =H 2,6,8 trimethyl 2 nonene-8-ol:R +R =-CH R3=H 2,6 dimethyl-2,9-decadiene-8-ol: R =-CH=CH R +R =H2,6,11-trimethyl-2,11-duodecadiene-8-ol:

CH2 R1=CH2CH2C\ R2 R =H CH: General Formula Ia:

General Formula Ic:

fl-citral (Neral or Geranial): General Formula Id:

p-Linalool: R=H B-Linalyl acetate:

The products formed in each case as a result of the oxidation reactionaccording to the invention which have a hydroperoxide group (II to 11dand III to IIId) are shown in the reaction scheme set out below. It hassurprisingly been found that in all cases investigated, the introductionof oxygen into the double bond to be oxidized occurs in such a way that60% of the reaction products represent compounds from the class of thegeneral Formulae II and the remaining from the class of the FormulaeIII.

As already mentioned, it is also extremely surprising that theselectivity of the oxygen attack on the C and C of the general formulaeis fully maintained as soon as a second double bond is introduced intothe molecule, and in fact in the vinyl or allyl position (C C to theoxygen function. Thus, the compounds of the general Formulae 1b, 10, andId could be transformed just as simply as I and Ia into the mixture oftheir hydroperoxide derivatives 11b to 11d and 11117 to IIId.

Hydroperoxide derivatives of the general Formulae II, IIb, IId or III,IIIb, and IIId in which R (or R in lid and IIId) represents a hydrogen,can be transformed by reaction of the hydroperoxide group with asaturated aqueous sodium sulphite solution in a manner known per se intoglycols of the general Formulae IV, IVb, and IVd and simultaneously V,Vb, and Vd. If the functional group in the 8-position is or contains ahigher oxidation stage than a hydroxyl group, the reduction can also becarried out in stages, by treating the hydroperoxide group in the 2- or3-position with triphenyl phosphine in the cold. For more detailedillustration reference is to be made to compounds of the type II or IIb,and III or IIIb, respectively, in which R or, as in the case of IId orIIId, R represents an acetyl group, while R and R contain H or alkylgroups. In another case, the partial reduction of the hydroperoxidegroup can also be carried out on compounds of the general Formulae Ilaor 110, in which R represents hydrogen, alkyl groups, a hydroxyl groupor alkoxy groups. It is also possible at will for hydroperoxidederivatives, the functional group of which in the 8-position has ahigher oxidation stage than a hydroxyl group, to be transformed in onestep into the glycols IV to IVd or V to Vd, if the reaction products ofthe photoxidation are reduced directly, if desired with the aid of LiAlHStarting from optically active starting material of the general FormulaeI, In and Id there are obtained according to the invention, at will,photoxidation products or partial reduction products or glycols havingthe same or opposite optical rotation. The degree of the activity ismerely dependent on the rotational value of the starting material.

The partial reduction products of the photoxidation of the glycols canbe separated from one another in a manner known per se by physical orchemical methods.

All glycols of the acyclic terpene series which are prepared by theprocess of the invention and more especially described herein are newand can be used as valuable perfuming substances on account of theirpleasing odor and their high fixing effect. Furthermore, the derivativeshydroxylated in the 2- or 3-position and having a functional groupdifferent from the hydroxyl group in the '8- position, such as thoseobtained with the partial reduction of the photoxidation of compounds ofFormulae I to Id constitute valuable perfumes and also are unknown.

The formulae and reaction schemes referred to above are set out below(see pages 17-21).

In order that the invention may be further understood, the followingexamples are given by way of illustration only:

EXAMPLE 1 A solution of 1000- g. of citronellol in 800 cc. of methanolis exposed to light under oxygen in the presence of 4 g. of Bengal pinkat room temperature in a lighting apparatus with an oxygen circulationand dipping lamp arrangement (HGH 5000, 900 watt). Oxygen absorption ispractically complete after liters have been absorbed in 1 8 hours. Thequantity corresponds to an oxygen absorption of 100% of the theoretical.

The strongly peroxidic reaction solution is poured into an ice-cooledsaturated aqueous solution of 2000 g. of sodium sulphite (20% excess ofthe theoretical) with vigorous stirring. After stirring for 1 hour in anice-cold condition, the reaction solution is heated for another hour to70 C. The organic layer is then separated from the aqueous phase and thereaction mixture is subjected to a vacuum distillation. In this way, aglycol mixture is obtained, having the following physical constants:

B.P. 9910l C.; N 1.4719; (1 0.9431;

a 133. Yield: 1080 g. of glycol mixture=98% of the theoretical.

EXAMPLE 2 A solution of 196 g. of (+)-citronellyl acetate in 780 cc. ofmethanol takes up 30.5 liters of oxygen over 6 hours in the presence ofl g. of Bengal pink in the experimental apparatus as described inExample 1. The reaction product is distilled off from the solvent and itis conducted slowly into a solution of 262 g. of triphenyl phosphine in400 cc. of dioxane with ice-cooling and vigorous stirring. By decantingoff or filtering with suction, the triphenyl phosphine oxide which hasformed is separated from the remaining reaction mixture, and the latteris further purified by removal of the solvent and vacuum distillation.The acetoxy-glycol mixture had the following physical constants:

11 1.4580; (1 0.9669; (m -{4.45. Yield: g.=88% of the theoretical.

50 g. of monoacetoxy-glycol are heated in 250 cc. of a half-normalalcoholic caustic potash solution for 1 hour under reflux. Thesaponification mixture is then poured into water and the organic layeris distilled in vacuo. The glycol mixture which is formed has thefollowing physical constants:

11 1.4725; d, 0.943; ot +1.38. Yield: 37 g.=95% of the theoretical.

EXAMPLE 3 308 g. of citronellal in 650 ml. of methanol are exposed tolight under oxygen in the presence of l g. of Bengal pink in theexperimental arrangement according to Example 1. After 10 hours, theoxygen absorption was practically completed at 42.25 liters. The workingup of the oxidation mixture was effected with sodium sulphite asdescribed in Example 1. A hydroxy-citronellal mixture is obtained whichboils at 83 and 90 C./0.020.05 mm. Hg. Yield: 292 g.=90% of thetheoretical.

50 g. of the crude photoxidation product freed from the solvent isintroduced dropwise and with vigorous stirring into an ice-cooledsuspension of 12 g. of LiAlH in 500 cc. of absolute ether. The reactionmixture is worked up in the usual way after stirring for 1 hour at roomtemperature. In this way, a glycol mixture is obtained which has thesame composition as that obtained according to Example 1. Yield: 49.5g.=98% of the theoretical.

EXAMPLE 4 120 g. of citronellic acid in 870 cc. of methanol arephotoxidized under the same conditions "as indicated in Example 1.Oxygen absorption after 6 hours: 17.85 liters=100% of the theoretical.

The reduction of the hydroperoxy acid was effected as indicated inExample 2.

Yield of oxyacid mixture: 122 g.=93% of the theoretical.

50 g. of the crude photoxidation mixture freed from the solvents isintroduced dropwise into a suspension of 15 g. of LiAlI-L; in 300 cc. ofether with vigorous stirring and cooling with ice and Worked up inaccordance with Example 3.

Yield of glycol mixture of the same composition as indicated in Example1: 36 g. =89% of the theoretical.

EXAMPLE 5 308 g. of geraniol in 650 cc. of methanol are photoxi dized inthe presence of 1 g. of Bengal pink in the experimental arrangementcorresponding to Example 1. Oxygen absorption after 9 hours 40 minutesis 46.75 liters=l% of the theoretical. After Working up the hydroxyhydroperoxide mixture with sodium sulphite solution in accordance withthe data given in Example 1, a glycol mixture is obtained which has thefollowing physical constants:

B.P.0 06 "D20 2 4 Yield: 278 g.=95% of the theoretical.

EXAMPLE 6 Under the conditions of Example and over a period of hours,300 g. of nerol took up 45.05 liters of oxygen. After reduction of thehydroxy hydroperoxide mixture with sodium sulphite solution, a glycolmixture is obtained, having the following physical constants:

B.P. 100107 C.; n 1.4907; (1 0.9718. Yield: 267 g.'=93% of thetheoretical.

EXAMPLE 7 308 g. of -Linalool is photoxidized in exactly the same way asindicated in Example 1. An oxygen absorption of 45.85 liters is obtainedwithin 10 hours 40 minutes, this corresponding to a quantitative oxygenabsorption for a double bond.

The hydroxyhydroperoxide mixture is worked up in the usual manner byreduction with sodium sulphite. The physical constants of the glycolmixture are:

Bvptmos 68-72 C.; "D (i4 0CD20'-2.5- Yield: 316 g.=93% of thetheoretical.

4 CO-R3 I R1 R2 Photosensitised Oxidation o (IQ R1 R1 ORE/k R1 R2 01ml""OOH II (60%) Reduction III (40%) IV V Partial Reduction 1 Reduction les d mu w P %m C M m m; d S V nfi R d 0 mm w mw HO m. H W. e d 0 mm v mR I C O O mf f I d e 6 J was Wm B U midm mm 1 0 C f e be WL f mo 5 m m bH V 0 nm Ill 0 \n4 R C W b H O W 0 m O 2 R 1 R Ma w P H n 0 0 I 6 1|. vR R .llllv 1 0 C/ 0 0 m n I mm mm H mm TM 0 F H R O R c 0 R V I I M \R l\R l C G 0 0 and 40% of the corresponding isomeric member selected fromthe group consisting of compounds of the formula IIld llv

wherein R is a member selected from the group consisting of hydrogen andacetyl.

2. A glycol mixture prepared by contacting citronellol with anoxygen-containing gas in the presence of Bengal pink as photo-sensitivecatalyst, subjecting the mixture to irradiation by light having a wavelength within the range of 350 to 590 mg and subjecting thephoto-sensitized oxidation product thereby obtained to reduction withsodium sulfite characterized by a boiling point of B.P. 99101 C.; 211.4719; df" 0.9431; ow -1.33.

3. An acetoxy glycol mixture prepared by contacting (+)-citronellylacetate with an oxygen-containing gas in the presence of Bengal pink asphoto-sensitive catalyst, subjecting the mixture to irradiation by lighthaving a wave length within the range of 350 to 590 my, and subjectingthe photo-sensitized oxidation product thereby obtained to reductionwith triphenyl phosphine oxide, characterized by the following physicalproperties: 11 1.4580; d 0.9669; oL +l.45.

4. An acetoxy glycol mixture prepared by contacting (+)-citronellylacetate with an oxygen-containing gas in the presence of Bengal pink asphoto-sensitive catalyst, subjecting the mixture to irradiation by lighthaving a wave length within the range of 350 to 590 my, and subjectingthe photo-sensitized oxidation product thereby obtained to reductionwith triphenyl phosphine oxide, and saponifying the reduction productthereby produced with 12 caustic potash solution, characterized by thefollowing physical properties: 1.4725; d 0.943; a +1.38.

5. A hydroxy citronellal mixture prepared by contacting citronellal withan oxygen-containing gas in the presence of Bengal pink, subjecting themixture to irradiation by light having a wave length within the range of350 to 590 my, and subjecting the photo-sensitized oxidation productthereby obtained to reduction with sodium sulfite, characterized by thefollowing boiling point: 83 to C./0.02-0.05 mm. Hg.

6. A glycol mixture prepared by contacting geraniol with anoxygen-containing gas in the presence of Bengal pink, subjecting themixture to irradiation by light having a wave length within the range of350 to 590 m and subjecting the photo-sensitized oxidation productthereby obtained to reduction with sodium sulfite, characterized by thefollowing physical properties: B.P. 105 C.; 11 1.4921; (1 0.9768.

7. A glycol mixture prepared by contacting nerol with anoxygen-containing gas in the presence of Bengal pink as photo-sensitivecatalyst, subjecting the mixture to irradiation by light having a wavelength within the range of 350 to 590 m and subjecting thephoto-sensitized oxidation product thereby obtained to reduction withsodium sulfite, characterized by the following physical properties: B.P.M5 -107" C.; a 1.4907; d 0.9718".

8. A glycol mixture prepared by contacting linalool with anoxygen-containing gas in the presence of Bengal pink as photo-sensitivecatalyst, subjecting the mixture to irradiation by light having a wavelength within the range of 350 to 590 my, and subjecting thephotosensitized oxidation product thereby obtained to reduction withsodium sulfite, characterized by the following physical properties: B.P.M5 68-72 C.; n 1.4788; d 0.9578; Ot -'2.5.

References Cited UNITED STATES PATENTS 3,014,047 12/1961 Bain et al260-489 OTHER REFERENCES Kenney et al.: J. Am. Chem. Soc., vol. 81,pages 4288- 4291 (1959).

LORRAINE A. WEINBERGER, Primary Examiner.

V. GARNER, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,382,276 May 7, 1968 Gunther Otto Schenck et a1.

It is certified that error appears in the above identified patent andthat said Letters Patent are hereby corrected as shown below:

Column 1, line 27, "citrolellol" should read citronellol line 37, before"ketone" insert a line 38, "C H should read C H O line 51, "should"should read would Column 3, line 2, "G. A. Schenck" should read G. 0.

Column 6, line 26, "133" should read l.33

Schenck line 66, "83 and 90" should read 83 to 90 Column 7, line 50 "Z5" should read 2 5 Column 8 lines 3 5 to 42 formula Va should appear asshown below:

same column 8, lines 45 to 52, in the right-hand column, the formulashould appear as shown below:

Column 9, lines-22 to 29, formula IIIc, should appear as shown below:

OOH

same column 9, lines 33 to 40 formula Vc should appear as shown below:

same column 9', lines 43 to 51, in the right-hand column, the formulashould appear as shown below:

Signed and sealed this 25th day of No vember 1969.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. WILLIAM E. SCHUYLER, JR. Attesting OfficerCommissioner of Patents

1. A MIXTURE OF COMPOUNDS COMPRISING 60% OF ONE MEMBER SELECTED FROM THEGROP CONSISTING OF COMPOUNDS OF THE FORMULA